The present invention relates to a developing apparatus applicable to various kinds of image recorders of the type using a two-component developer and, more particularly, to a device for supplying a toner to a developer stored in a developing apparatus from a toner cartridge which is removably loaded in a toner tank that is mounted on the developing apparatus.
In an electrophotographic copier, facsimile machine or similar image recorder, a toner contained in a developer which is stored in a developing apparatus is sequentially consumed as the developing apparatus is repeatedly operated. Therefore, a fresh toner has to be supplied to the developer in the developing apparatus every time a predetermined number of copies are produced or every time the toner density in the developer which is sensed is lowered to a predetermined value. A predominant implementation for the supply of fresh toner into a developing apparatus is a disposable toner cartridge which is filled with a fresh toner. The toner cartridge is removably loaded in a toner tank which is mounted on the developing apparatus, so that the fresh toner may be fed into the developing apparatus via a slot of the cartridge. When the toner in the toner cartridge is fully consumed, the empty cartridge is removed from the toner tank and discarded and, then, a new toner cartridge is loaded in the tank.
A prerequisite with such a disposable toner cartridge is that it be produced with a minimum of cost. Preferably, therefore, a toner cartridge should be commonly applicable to various types of developing apparatuses. On the other hand, some machines are operable with a particular kind of toner only and therefore needs an exclusive toner cartridge containing such a toner. With this kind of machine, it is necessary that a toner cartridge other than the exclusive toner cartridge be prevented from being inserted into a toner tank which is mounted on a developing apparatus of the machine. While some different approaches have heretofore been proposed to eliminate such inadvertent insertion of a toner cartridge of alien kind, they are complicated in construction and cannot fully eliminate the insertion of a toner cartridge of alien kind and, moreover, force a person to perform troublesome manipulations.